Use of northern hardwoods in glued-laminated timber: a study of bondline shear strength and resistance to moisture
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ORIGINAL
Use of northern hardwoods in glued-laminated timber: a study of bondline shear strength and resistance to moisture Alexandre Morin‑Bernard1,2 · Pierre Blanchet1,2 · Christian Dagenais1,2,3 · Alexis Achim2 Received: 16 September 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The growing demand for engineered wood products in the construction sector has resulted in the diversification of the product offer. Used marginally in structural products in North America, northern hardwoods are now attracting a growing interest from industry and policy makers because of their outstanding strength as well as their high availability and distinctive appearance. Currently, there is no standard in Canada governing the use of hardwoods in the manufacturing of gluedlaminated timber. As part of a larger project aiming to assemble the basic knowledge that would lead to such standard, the specific objective of this study was to assess the shear strength in dry and wet conditions of assemblies made from different hardwood species and structural adhesives. Results suggest that a mean shear strength as high as 20.5 MPa for white oak, 18.8 MPa for white ash and respectively 18.2 MPa and 17.4 MPa for yellow birch and paper birch can be obtained in dry conditions. The choice of adhesive did not affect the dry shear strength of these specimens, but differences were observed in wet conditions. Specimens bonded with melamine-formaldehyde adhesive had generally the highest wet shear strength and wood failure values. These results also highlight the important influence of wood density on the percentage of failure that occurs in wood and, to a lesser extent, on shear strength. Further investigations on finger joint strength and full-size bending tests will allow confirming the potential for the investigated species to be used in glued-laminated timber.
1 Introduction The currently growing demand for engineered wood products in the construction sector is largely attributable to their outstanding ecological performance. The substitution of materials having a larger ecological footprint, such as steel and concrete, by structural engineered wood products like glued-laminated timber (GLT) has proven to be effective in minimizing the environmental impacts of the building sector (Thormark 2006). In addition to sustainability-related arguments, building designers also tend to choose wood products because of their aesthetics (Gaston 2014; Gosselin et al. 2016; Laguarda Mallo and Espinoza 2015; Markström * Alexandre Morin‑Bernard alexandre.morin‑[email protected] 1
NSERC Industrial Chair on Eco‑Responsible Wood Construction, Laval University, Quebec, QC G1V 0A6, Canada
2
Renewable Materials Research Centre, Laval University, Quebec, QC G1V 0A6, Canada
3
Building Systems, FPInnovations, Quebec, QC G1V 4C7, Canada
et al. 2018). Aware of the market opportunities as well as of the lack of high value-added opportunities for some wood species, industry and policy makers from several jurisdictions have recent
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